Japanese Unexamined Patent Publication No. 2004-314550 discloses a filament winding device adapted to wind a plurality of fiber bundles around a liner. The filament winding device includes a supporting section adapted to rotatably support a liner and be movable in an axial direction of the liner, and a helical head adapted to carry out helical winding (winding a fiber bundle in a direction substantially parallel to the axial direction of the liner) on the liner.
The helical head includes a plurality of fiber bundle guides adapted to guide each of the plurality of fiber bundles to the liner, and a spreading guide having an inner peripheral surface that spreads (i.e., opens) a width of the plurality of fiber bundles guided by the plurality of fiber bundle guides. The inner peripheral surface of the spreading guide has a circular shape when seen from the axial direction. The fiber bundle travels while making contact with the inner peripheral surface of the spreading guide to be rubbed and opened by the inner peripheral surface of the spreading guide.
As described in Japanese Unexamined Patent Publication No. 2004-314550, if the inner peripheral surface of the spreading guide has a circular shape (i.e., curved line across the entire periphery), the fiber bundle makes contact with a circular arc shaped portion. Hence, the fiber bundle is less likely to become flat even if rubbed and opened and is less likely to spread in the width direction (peripheral direction of the inner peripheral surface). Thus, when the plurality of fiber bundles are wound around the liner, a gap in a peripheral direction easily forms between the fiber bundles and the strength of the liner may lower.
It could therefore be helpful to enable the width of the fiber bundle to be easily spread at the time of opening.